Lexington Weather

Area Forecast Discussion
for Boston / Norton, MA

        
000
FXUS61 KBOX 151111
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
711 AM EDT Mon Apr 15 2024

.SYNOPSIS...
High pressure establishes itself over Southern New England
through midweek. It will bring abundant sunshine, dry weather,
seasonably mild temperatures and northwest breezes through
Tuesday. Dry Wednesday through at least mid-day Thursday before more 
unsettled conditions develop late week. Above normal temperatures 
return

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

7 AM Update:

Patchy fog, dense in some spots, will dissipate quickly this
morning with daytime heating. Winds will remain rather light
through about 10am before mixing really kicks into gear, after
which time gusts to 20kt are possible. After collaborating with
ZBW, winds "off the deck" (500-2000ft off the surface) appear
strong enough to stave off the seabreeze mentioned by the
previous forecaster at Boston Logan, but it is quite possible
that winds just offshore shift the south briefly late this
morning. 

A very isolated spot shower is possible along the pseudo 
seabreeze boundary on the south coast as winds switch more to 
the SW over the southern waters. Otherwise, diurnal cu 
development will yield partly cloudy conditions, especially 
across the eastern half of the CWA. 

All in all, it's shaping up to be a beautiful day across
southern New England! 

350 AM Update:

Key Points: 

* Areas of fog to dissipate through mid-morning as winds pick up.

* Variable amounts of clouds, but dry weather and milder than normal 
  temperatures. Though coastal sea breezes could develop, expect 
  breezy NW winds around 20-25 mph for most.

Slow-moving frontal boundary lies along the immediate RI/MA South 
Coast, with residual showers mainly offshore. Thus most of Southern 
New England is stuck in a very weak pressure gradient with winds 
being light to calm. That's also led to an expanding field of 
radiation fog where winds are calm, particularly in northern CT and 
western and central MA where some sites are seeing visbys as low as 
one quarter mile. Current temperatures were in the lower to mid 40s, 
except upper 40s for the coastal areas. 

We're expecting dry weather and other than variable amounts of fair 
weather clouds and northwest breezes, it should a generally pleasant 
Monday for much of Southern New England today. But until winds pick 
up, areas currently seeing foggy conditions will continue to see fog 
around. Expect by mid morning that fog will begin to dissipate, as 
this is when WNW breezes should start to develop. Coastal sea-
breezes on both coasts also look to develop briefly too (E/ESE for 
immediate coastal eastern MA and S/SW for the RI/MA south coast) in 
this light sea level pressure pattern; but it should be short lived 
as stronger NW flow eventually takes hold.  

While coastal areas and around the higher terrain will see high 
temperatures in the upper 50s to lower 60s, away from these areas we 
should see highs reach well into the 60s to lower 70s. Overall 
pleasant conditions for those heading into Boston today, but there 
could be a pretty significant difference in temperature along the 
immediate shore/Boston Harbor area (mid 50s) compared to the western 
suburbs (mid 60s) if the sea breeze does develop.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
350 AM Update:

Tonight:

Cyclonic flow aloft redevelops tonight across Southern New England, 
with decreasing NW winds and continued dry weather. A few models 
generate some isolated showers passing near or south of Nantucket as 
a weak disturbance over the mid-Atlantic passes near our coastal 
waters, but favoring dry weather with any showers over the waters. 
Lows in the mid 30s to lower to mid 40s. 

Tuesday: 

Tuesday shaping up to be a beautiful day, generally similar to 
today. Deep dry air aloft favors abundant sunshine and high 
temperatures in the upper 50s to the mid to upper 60s. That will 
also favor deep mixing and falling dewpoints during the diurnal 
heating period, and it is possible that dewpoints could dip into the 
upper 20s with efficient mixing. Will see northwest winds increase 
again with gusts around 20-25 mph, with any sea breezes restricted 
to the immediate coastlines. Because of the combo of deep dry air 
and the NW breezes, we could see a period of elevated fire weather 
concerns for Tuesday. See the Fire Weather section for more details.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Highlights:

* Unsettled pattern with more dry periods than wet

* Very pleasant spring temperatures mid week transition to seasonable 
  by late week and next weekend. 

Mid level ridging builds into the region starting very early 
Wednesday, cresting Thursday before moving seaward on Friday as 
cutoff low centered about the Dakotas weakens and moves northeast 
into the Great Lakes region. Broader trough and a few shortwaves 
eject out of Canada late week and early next weekend.

Wednesday and Thursday...

Surface high pressure located over the southern waters, with 
strength during the day on Wednesday, will eat away at the advancing 
rain shield/front associated with aforementioned cutoff low advecting 
into Ontario. This will lead to a mainly dry period Wednesday into 
Thursday morning with more substantial cloud cover compared to 
Tuesday, but as high pressure weakens Thursday, should start to see 
a few light showers move into the western zones of the CWA sometime 
around 18Z. Model soundings corroborate the drying trend for mid 
week showing a very dry column both at the surface and above 700mb 
with some slight saturation at the top of the mixed layer; the 
column not expected to saturate and produce precip in our western 
zones until after the lunch hour Thursday and very late in the 
evening for the eastern half of the CWA. Even with light showers 
around, QPF looks rather limited with this wave with a significant 
majority of guidance forecasting less than a quarter of an inch of 
rain; there are a few outliers, namely the operational GFS, that are 
more amplified, producing up to a half inch of rain. 

There is a bit of uncertainty regarding temperatures during the 
period, though Wednesday looks milder that Thursday. Mixing will be 
healthy on Wednesday, to about 800mb, with northwest 925mb flow. 
Expecting another day of highs in the 60s before winds shift to 
onshore for Thursday. Onshore flow, SSTs in the 40s, and more robust 
cloud deck will yield much cooler temps Thursday, with some 
guidance, like the GFS and MAV, forecasting highs in the 
upper 40s to low 50s. 

Friday into the Weekend...

With broad trough centering over New England, expecting near to 
slightly below normal temperatures and another round of unsettled 
weather for the weekend. While still several days away, global 
guidance shows a few shortwaves moving through, the first Friday 
into Saturday and another late in the weekend, that like bring on 
and off showers to the region. There remains plenty of time between 
now and late week for forecast details to be sussed out, so stuck 
with the NBM for this period.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

Low - less than 30 percent. 
Moderate - 30 to 60 percent. 
High- greater than 60 percent. 

12z TAF Update: 

Today: High confidence. 

Mainly VFR, with any sub-VFR fog that developed overnight to 
trend VFR shortly after 12z as W/WNW winds start to increase. 
Will see SCT-BKN VFR decks today (bases 045-070, on the higher 
end of that range in aftn). 

With a light pressure gradient to start, winds are a little 
tricky/nuanced. Light W winds begin the morning before the 
increase in WNW speeds/gusts; that could put a period of brief 
sea- breezes at south-coastal sites (SWlys) and at BOS (SElys 
4-7 kt between 14-16z indicated with TEMPO). Anticipate after 
16z that winds become WNW and increase to around 10-15 kt with 
gusts 20-25 kt all areas, strongest over the terrain.

Tonight: High confidence.

VFR. Outside chance at a shower affecting ACK late
tonight/midnight. WNW winds continue but slacken to around 5-8 
kt.

Tuesday: High confidence. 

VFR mainly SKC. NW winds increase to 8-12 kt with gusts to 20
kt starting mid-morning and continuing til sundown.

KBOS TAF...High confidence in TAF. VFR with SCT 050 bases. Could
see a possible sea-breeze develop around 14-16z but would be
brief as prevailing WNW gradient wins out after 16z, with 
WNWlys 10-14 kt with gusts in the low-20s kt range.

KBDL TAF...High confidence in TAF. Mainly VFR. There could be a
brief period of IFR BR/BCFG near the airport early this morning
but will dissipate shortly after sunrise as W/WNW winds increase
to around 10 kt.

Outlook /Tuesday Night through Friday/... 

Tuesday Night: VFR. 

Wednesday: VFR. Slight chance SHRA.

Wednesday Night through Thursday: VFR. Breezy. Chance SHRA.

Thursday Night: VFR. Breezy. Slight chance SHRA.

Friday: VFR. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels:

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent. 

355 AM Update: 

SCAs remain in effect mainly for residual seas still around 4-6
ft. However decreasing trends to seas are expected. 

Mainly S to SSW winds around 10-15 kt are expected today and 
tonight, though could turn easterly along the immediate
shore/harbors today. For Tuesday, expect northwest winds around
10-15 mph in gusts. Seas 4-6 ft initially decrease today and
becoming 2-4 ft tonight into Tuesday.

Outlook /Tuesday Night through Friday/... 

Tuesday Night through Wednesday: Winds less than 25 kt. 

Wednesday Night: Winds less than 25 kt. Slight chance of rain
showers. 

Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas locally approaching 5 ft. Slight chance of rain
showers. 

Thursday Night through Friday: Winds less than 25 kt. Areas of
seas approaching 5 ft. Slight chance of rain showers.

&&

.FIRE WEATHER...
350 AM Update: 

We could have a period of elevated fire weather concerns for
Tuesday. Abundant sunshine bringing high temperatures in the 
60s combined with a well mixed atmosphere bringing dewpoints
into the upper 20s to lower 30s support relative humidities
around 25 to 30 percent, especially for interior CT, MA and RI.
NW winds will also become a little breezy with gust speeds
around 20 to 25 mph. The one potential deterrent is how
saturated soils are. That said, we will consult with our state
forestry partners regarding the need for any fire weather
statements or products.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 PM EDT this afternoon for 
     ANZ232>235-237-250.
     Small Craft Advisory until 8 PM EDT this evening for 
     ANZ254>256.

&&

$$

SYNOPSIS...Loconto/KS
NEAR TERM...Belk/Loconto/KS
SHORT TERM...Loconto
LONG TERM...KS
AVIATION...Loconto/KS
MARINE...Loconto/KS
FIRE WEATHER...Loconto